Schering-Plough Submits New Drug Application (J-NDA) in Japan for PEG-INTRON(R) and REBETOL(R) Combination Therapy for Hepatitis C

April 22, 2004

Schering-Plough Submits New Drug Application (J-NDA) in Japan for

PEG-INTRON® and REBETOL® Combination Therapy for Hepatitis C

KENILWORTH, N.J., April 21 /PRNewswire-FirstCall/ -- Schering-Plough

Corporation (NYSE: SGP) today announced that Schering-Plough K.K., the

company's subsidiary in Japan, has submitted a New Drug Application (J-NDA)

to

the Ministry of Health, Labor and Welfare (MHLW) seeking marketing approval

for PEG-INTRON® (peginterferon alfa-2b) Powder for Injection for use in

combination with REBETOL® (ribavirin) Capsules for the treatment of

chronic

hepatitis C. The MHLW will provide a priority review of the application.

If

approved, PEG-INTRON and REBETOL will be the first and only pegylated

interferon-based combination therapy approved in Japan for treating chronic

hepatitis C.

Hepatitis C is estimated to affect some 2 million people in Japan,

according to MHLW. It is the leading cause in Japan of chronic liver

disease,

cirrhosis and hepatocellular carcinoma, and is associated with more than

30,000 deaths there annually. Hepatitis C is the most common reason for

liver

transplant in major world markets, including Japan, according to a study

conducted by the World Health Organization (WHO).

Schering-Plough K.K. currently markets REBETOL in Japan for use in

combination with INTRON® A (interferon alfa-2b, recombinant) Injection for

chronic hepatitis C. INTRON A also is approved in Japan for use as

monotherapy for hepatitis C, hepatitis B and several cancer indications.

PEG-INTRON is a longer-acting form of INTRON A that uses proprietary PEG

technology developed by Enzon, Inc. (Nasdaq: ENZN) of Bridgewater, N.J.

PEG-INTRON, recombinant interferon alfa-2b linked to a 12,000 dalton

polyethylene glycol (PEG) molecule, is a once-weekly therapy that is

designed

to achieve an effective balance between antiviral activity and elimination

half-life. Schering-Plough holds an exclusive worldwide license to

PEG-INTRON.

INTRON A is a recombinant version of naturally occurring alpha

interferon,

which has been shown to exert both antiviral and immunomodulatory effects.

Schering-Plough markets INTRON A for 16 major antiviral and anticancer

indications worldwide.

REBETOL is an oral formulation of ribavirin, a synthetic nucleoside

analog. Schering-Plough has worldwide rights to market oral ribavirin for

hepatitis C through a licensing agreement with Valeant Pharmaceuticals

International (NYSE: VRX), formally ICN Pharmaceuticals, of Costa Mesa,

Calif.

DISCLOSURE NOTICE: The information in this press release includes

certain

" forward-looking " statements concerning PEG-INTRON and the regulatory

process

in Japan, the market for drugs to treat hepatitis C and Schering-Plough's

products. Forward-looking statements are subject to risks and

uncertainties,

which may cause actual results to differ materially. These risks and

uncertainties include product availability, current and future branded,

generic and OTC competition, the regulatory process for new products and new

indications, market acceptance of new products and new indications, timing

of

trade buying, and patent positions. For further details and a discussion of

these and other risks and uncertainties, see the company's past and future

Securities and Exchange Commission filings, including the company's 2003

10-K

filed Feb. 26, 2004.

Schering-Plough K.K., based in Osaka, is a wholly owned subsidiary of

Schering-Plough Corporation, a research-based company engaged in the

discovery, development, manufacturing and marketing of pharmaceutical

products

worldwide.

SOURCE Schering-Plough Corporation

Web Site: http://www.schering-plough.com

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April 22, 2004